Thermo- and fluiddynamics of lubricants with CO{sub}2 at transcritical conditions

摘要

While fluorinated hydrocarbons as HFC in cooling circuits are in the subcritical state, carbon dioxide is both sub- and supercritical with respect to pressure and temperature. The viscosity decrease caused by solubility of Co{sub}2 in lubricants under high pressure might give cause for wear in a compressor. For the proper design and operation of refrigeration circuits, the knowledge of phase behavior and viscosity behavior of lubricants with CO{sub}2 is essential. Results of basic investigations on three different synthetic lubricants exhibit different types of phase behavior with CO{sub}2, are presented and discussed with respect to typical operation conditions.